Which type of defect is observed in crystals like $NaCl$ and $KCl$?

Non-stoichiometric cuprous oxide,$Cu_{2}O$ can be prepared in the laboratory. In this oxide,the copper to oxygen ratio is slightly less than $2:1$. Can you account for the fact that this substance is a $p$-type semiconductor?

Due to the Frenkel defect,the density of a solid $..........$

$F$-centres are formed in $NaCl$ crystal if it is heated with $Na$ vapour. The above is due to

The pyknometric density of sodium chloride crystal is $2.165 \times 10^3 \ kg \ m^{-3}$ while its $X$-ray density is $2.178 \times 10^3 \ kg \ m^{-3}$. The fraction of unoccupied sites in sodium chloride crystal is

Use the appropriate symbols $T$ (True) or $F$ (False) for the following statements regarding defects in solids:
$(1)$ Frenkel defect arises due to the arrangement of cations and anions with a very small difference in size.
$(2)$ Frenkel defect can be called a dislocation defect.
$(3)$ $F$-centers arise due to the migration of electrons released from metal atoms into the crystal lattice.
$(4)$ Physical properties of the crystal do not change due to Schottky defect.